Well Actually, sort of yeah!

It was never so severe as to outright prevent shipping, but certainly coastal communities were frightful of American warships, and the RN did have to dispatch ships to both escort convoys and hunt down the foe.

Perhaps the most famous man involved in the whole effort is none other than John Paul Jones. In early 1777 he took the USS RANGER into the Irish Sea from Brest, in order to visit what mayhem he could to aid the Colonial cause. He raided in several locations, from old town of Whitehaven in Britain, to Scotland and an attempt to seize the Earl of Selkirk. However the most notable event from his time in RANGER came when he sought to fight the sloop HMS DRAKE off Carrickfergus, and in a running duel managed to capture the ship and take her as a prize.

That summer then he took command of the larger BONHOMME RICHARD and a squadron of some half dozen American or Privateer warships to raid again, this time in support of eventually abandoned French and Spanish attempts to concentrate naval power against Britain and threaten invasion. This time the squadron passed around the North of Scotland and began raiding down the eastern coast of England. Where on the 23rd of September the force encountered a convoy under the protection of the armed hire ship COUNTESS OF SCARBOROUGH, and the 44 gun frigate HMS SERAPIS. In a close fought struggle RICHARD would sink, but the Americans would carry the day and capture SERAPIS. This was also the battle where Jones reported to utter his famous "I have not yet begun to fight!".

So yes there was an American naval presence that was at least for a few years, credible and real, in the Irish Sea during the American Revolution.